Genentech's Rituxan Faces Stiff Competition

HuMax is currently in phase III trials for the treatment of both CLL and NHL and phase II trials for rheumatoid arthritis. Its CLL trial targets patients who have not responded to Rituxan and chemotherapy. In other words, these are very sick people. The FDA has fast-tracked HuMax for CLL. Should the drug show efficacy on such a difficult patient set, it should very well be able to help others with CLL.

Of Mice, Men and Market Share

A HuMax approval in 2007 could take a large chunk of Rituxan's market share in CLL. It also may spark off-label uses in NHL and rheumatoid arthritis.

"I think a very high percentage of Rituxan's [sales] has been off label," Genmab's CEO Dr. Lisa Drakeman says. "So if people start believing in CD20 therapy for a variety of diseases and we haven't finished the clinical studies to file for approval on all of those, it's possible that, at least in the United States, people would use these products off label, because we've seen that historical pattern."

Drakeman says the market opportunity could be worth as much as $7 billion a year and it's growing. "Rituxan essentially has the market to itself. We have an antibody that we hope has some advantages."

But Dr. Kip Benyunes, Genentech's group director of clinical hematology and oncology, is not yet convinced. He points out that while the HuMax data may be tantalizing, they measure only response rates. "Over the last 10 years, we've moved on beyond response rates to clinically important endpoints, which is progression-free survival in lymphoma." Benyunes stresses that Rituxan has been proven to improve survival three and five years out.